Heating plant employed in different industries tends to operate at increasingly growing temperatures, which imposes stringent requirements on the methods of controlling the state of lining in the course of operation so as to obtain exact information on the span of trouble-free operation of each individual unit.
There is known a device for gauging the thickness of refractory lining (cf. U.S. Pat. No. 3,315,076, cl. 250-83,3, of 1967), comprising a lining thickness pulse transducer mounted on that portion of the lining which is subjected to thickness measurements. The transducer incorporates a fast neutron source, an ionizing radiation detector, and a protective shield interposed between the source and the detector. The source, shield and detector are accommodated in a sealed housing. The device further includes an electric pulse measuring unit connected to the lining thickness pulse transducer. The ionizing radiation detector is a spectrometer-type gamma ray detector. The device under review is disadvantageous in that the gamma radiation is largely absorbed by the lining material, which affects the accuracy of measurements in the case of thick linings.
In addition, the small cross-section of activation and radiative capture of neutrons by atomic nuclei of elements contained in refractory lining materials call for a fast neutron source capable of producing a neutron flux of about 10.sup.5 to 10.sup.6 neutron/cm.sup.2 .multidot.sec on the lining surface. To comply with this requirement, one must use complicated equipment and unwieldy biological protection shields.
The device in question is further disadvantageous in that the spectometer-type gamma radiation detector can operate only within a relatively narrow range of temperatures; this accounts for the complicated design of the lining thickness pulse transducer, as well as for difficulties involved in arranging the transducer on the lining of an operating unit.